Of keyboards and terminals

Of keyboards and terminals

[Stefan Monnier]

We currently have a slightly odd situation:

In 99% of the cases, each keyboard object has a single terminal object
and each terminal has a single keyboard.  But in some rare cases,
several terminals can share a single keyboard.  See the same_x_server
function in xterm.c.

This can be the case when you have different connections to the same
X server.  This can happen if you make a frame on unix:0 and then
another frame on localhost:0 and yet another on <myhostname>:0.  This is
not very common, tho.

A more significant situation is when you have a multi-screen setup such
that you can make a frame on :0.0 and another on :0.1 and yet another
on :0.2.  These *require* separate terminal objects (and separate
X connections).

So in those particular cases, Emacs shares a single keyboard object
between those different terminal objects.  The intent of sharing
a single keyboard has mostly to do with the fact that once a command is
started, Emacs is put into "single-keyboard" mode so that all the input
coming from other keyboards is temporarily delayed.

As far as I can tell, this is the only benefit.

The problem is that variables like function-key-map are not
terminal-local (as people often think) but keyboard-local instead.
OTOH they're initialized per-terminal, and there is generally some
confusion between pr-keyboard and per-terminal objects and actions.

So I'm thinking of eliminating the special case that shares the keyboard
among different X11 connections to the same underlying server: the
sharing does make sense, but its benefit doesn't seem to justify the
resulting complexity.


        Stefan

Re: Of keyboards and terminals

[Richard Stallman]

    So I'm thinking of eliminating the special case that shares the keyboard
    among different X11 connections to the same underlying server: the
    sharing does make sense, but its benefit doesn't seem to justify the
    resulting complexity.

The one real benefit of having a single keyboard has to do
with the locking between keyboards.  The current behavior is correct
in the case of multiple screens with one keyboard.

Also, the fact that many variables (in particular, such as
overriding-terminal-local-map) are keyboard-local is right.
The word "terminal" in the name is misleading, but that means
we should change the name, not change the (correct) behavior.